Knocking sound engine.. need help
 

Hey Guys,

So I started hearing the hissing type rattle under acceleration only. Sounds like if you put bbs in a tin can and shook the can real fast. Only with throttle. Goes away with foot off gas. Happens driving and neutral but less in neutral.

I popped under the car and gave it some gas with a long lever to see if I could pinpoint the area. Kind of looks like it’s coming from either where the trans meets the engine or somewhere around the engine oil pan. Can’t tell.

But what was even more concerning is when I was revving the engine up to hear the noise, when the engine would slow down from like 2.5k to idle quickly, I’d hear a pretty audible “knock knock thud” coming from what sounds like directly under the engine.

I was able to repeat the noise several times. Didn’t do it every time but probably 2 out 3 times on average.

I’ve done a ton of maintenance recently so hard to pinpoint. But I did do a full trans fluid transfer using the pump method with Valvoline max life, 150 miles ago. I checked the fluid level after using the “warm hand” procedure. Pretty sure the fluid level is correct.

The knocking scares the heck out of me and I have to drive to Vermont tomorrow (500 miles).

Any thoughts are welcome.

Is the check engine light on? If so get codes read. Had something similar and turned out to be a failing OCV (timing solenoid). Had it replaced and issue never came back. Code should tell you which bank, this which solenoid needs to be replaced.

Thanks for the quick reply.

Was there a knocking noise that prompted you to look further into it or just the code? I don’t have a code right now. Last one was a P0420 code but replaced an o2 sensor a few days ago.

The knocking freaks me out. I’ve put about $6k into her after I bought the rig 3 months ago. She’s finally looking good. Can’t have an engine fail on me

What’s the sound of like a failing rod, etc? Never had an issue with that. Someone please talk me down off the ledge!!

Was on a road trip with family and stopped for lunch, when got back in truck started it up felt a little rough. Pulled out of parking lot and could tell the power wasn't there and seemed to sputter, then stopped at a set of lights and engine light came on and could tell timing was off.

We continued to the beach we were heading to and when I pulled up to the gate it started to knock horribly, very scary sound.

When we left I chance it and seemed to drive better at speed, so on Highway was fine. The next day seemed ok, but timing would go off every so often. So had the code checked and mechanic pulled the suspect OCV, tested it and couldn't get it to fail. Cleaned it and put it back in and was fine for a couple days then came back with a vengeance, worse knock than before.

Had the timing chain checked for possibly stretching and was fine, replaced the OCV and all is well.

I feel for ya man, after a year of owning mine I had to replace the head gasket, was not happy about the expense but decided to commit to the vehicle. Been 6 years now and still happy with it, that was the only large expense I had but I won't lie, had plenty of other's that up to roughly 10 grand in total. Bought it believing the Toyota reliability hype but quickly realized that old is old no matter what make and shit will go wrong and I've just accepted that. Still cheaper than buying new. :)

Good luck man.

Heard a noise like that years ago on a friend's vehicle...bolts between the flex plate and torque converter were loose.

I appreciate the detailed story! Wow that was a lot of investigating but sounds like a positive outcome.

Do you have the v6 or v8 out of curiosity?

No check engine code yet. Maybe time to take her in... ughh

I read something about the flex plate somewhere.

How is this diagnosed? And how did your buddy figure out that’s what it was?
Thanks

Something I noticed too..

It only happens when I rev up quickly and let off the gas quickly.

Also have only been able to recreate the sound while in park or neutral. Do these engines knock when spinning down quickly? Any techs out there??

i would take it to somewhere with a rlift, get it up, and get a stethoscope on it see if you cant pinpoint the noise more.

subscribing out of curiosity.

It's a V6.

So the knocking is happening often for you? If so probably best to have looked at. If it's the OCV not too expensive and could actually replace yourself, didn't look too difficult.

He had the car up on ramps and jack stands and ran it in gear (very dangerous and not recommended of course) so he could locate the noise more precisely - which you've already done. Then he removed the access panel and found the flex plate bolts loose....tightened them all to specification and the noise was gone.

any updates on this? I have an 06 v8 4wd with only 160k mile with an intermittent knocking sound. I dismissed it as rod knock but there is no metallic particulate in the oil. curious if anything is related here before I pull the engine.